To date, most studies of outpatient rehabilitation have not adjusted for patient comorbidity, in part, because comorbidity indices were not available in outpatient rehabilitation datasets. The Functional Comorbidity Index (FCI) developed to predict functional status (FS) was recently added to the Focus on Therapeutic Outcomes (FOTO) outpatient rehabilitation database. The FCI was developed using cross-sectional data, and we do not know if observed relationships will persist in longitudinal analysis. Nor do we know if FCI summary scoring is appropriate across a range of impairments. Lastly, we do not know if FCI use would improve predictive models for service utilization. The Specific Aims of this study are to (1) examine the association between the FCI and functional status (FS) at intake and discharge, (2) examine the impact of FCI on discharge FS when added to comprehensive predictive models of FS, and (3) examine the impact of FCI on the number of visits utilized, when added to comprehensive predictive models. This is a prospective, longitudinal, cohort study. The 50,000 sample will be drawn from the FOTO database. FS data will be collected using 9 impairment/condition specific CATs: orthopedic impairments of the lumbar spine, hip, knee, foot/ankle, shoulder, elbow, and wrist/hand and cervical spine, or neurological conditions. The FCI's association with both intake and discharge FS for each impairment group, and the association between overall FCI score, as well as FCI scores calculated using impairment specific weighting will be examined. Separate comprehensive multivariate models for discharge functional status and number of visits will be developed. The PIs will test the hypothesis that models including the FCI will perform better than models without the FCI. Models using original FCI summary scoring will be compared to models using impairment specific weighted scoring. [unreadable] [unreadable] Public Health Relevance: Outpatient rehabilitation data is already being used for provider profiling and the development of pay for performance models. To date, studies using this data have not adjusted for comorbid conditions. Lack of adjustment for comorbidity in quality measurement may foster an environment in which providers avoid treating patients with comorbid conditions who may have poorer response to treatment. A new comorbidity index was recently added to a large outpatient rehabilitation dataset offering the opportunity to examine its validity and potential contribution to risk adjustment modeling. Costs for outpatient rehabilitation services have increased dramatically and payers are seeking ways to get better value in purchasing. In order to develop alternative payment systems based on quality of care, risk- adjustment processes that adjust for comorbid conditions need to be developed. Lack of adjustment for comorbidity in quality measurement may foster an environment in which providers avoid treating patients with comorbid conditions who may have poorer response to treatment. [unreadable] [unreadable] [unreadable]